Magnetic Test (MT) is a non-destructive test method for the detection of surface and sub-surface discontinuities in ferrous materials.Â The test method involves application of magnetic field externally or applying electric current through the material which in turn produces magnetic flux in the material.Â
Simultaneously, visible ferrous particles on sprinkled or sprayed on the test surface. The presence of a surface or near surface discontinuities in the material causes distortion in the magnetic flux which in turn causes leakage of the magnetic fields at the discontinuity. The magnetic particles are attracted by the surface field in the area of the discontinuity and adhere to the edges of the discontinuity appearing the shape of the discontinuity.
Magnetic particle test (MT) is very sensitive test method. It can detect tight in-service fatigue cracks in rotating parts or creep cracks on steam piping. Magnetic Particle Inspection cannot be used for non-ferrous materials and non-magnetic ferrous materials such as austenitic stainless steels.
- Can detect both surface and near subsurface indications
- Can inspect parts with irregular shapes easily
- Pre-cleaning is not as critical as for some other inspection methods
- Fast method of inspection and indications are visible directly on the specimen surface
- Considered low cost compared to many other NDT techniques
- Very portable inspection especially when used with battery powered equipment